1. Field of the Invention
This invention relates to an injection metal mold for so-called undercut molding wherein molding is effected by pouring of a material such as a synthetic resin material into a metal mold body in which a slide core different from a core of the metal mold body is projected to a lower edge portion of an article to be molded.
2. Description of the Prior Art
Conventionally, a metal mold body having an article forming section for forming an article itself therein is formed separately from an opening and closing mechanism for opening and closing the metal mold body and a molding machine body including an injecting and pouring mechanism for pouring a material such as a synthetic resin material into the article forming section of the metal mold body. Meanwhile, the metal mold body and an outer frame mechanism for mounting the metal mold body on the molding machine body are conventionally formed in an integral relationship with each other.
However, since it is very uneconomical to prepare for each type of articles to be molded a metal mold including a metal mold body having an article forming section therein and an outer frame mechanism, it has been a common practice in recent years to prepare a common outer frame mechanism in the form of a metal mold fixing frame mechanism, and further prepare a metal mold body having an article forming section therein for each of different types of articles to be molded and mount one of the metal mold bodies thus prepared on the common outer frame mechanism in the form of a metal mold fixing frame. In other words, one of metal mold bodies which are prepared for different types of articles to be molded and each has an article forming section therein is arbitrarily mounted or replaced on an outer frame mechanism in the form of a metal mold fixing frame.
However, since undercut molding must be effected while an undercut portion forming slide core other than a core side metal mold element which is a body of an article forming section is projected into a cavity of the core side metal mold element, a slide mechanism section for retracting the undercut portion forming slide core from an article forming recess to permit removal of a molded article in response to movement of the metal mold body when the metal mold body is opened for removal of a molded article must be provided on an outer edge of the molded article forming section of the metal mold body.
Such a slide mechanism section for the undercut portion forming slide core as described just above, however, requires a considerable number of components including an angular pin and a corresponding angular pin hole as well as a slider block for slidably moving the slide core. As the slide mechanism section having such a structure as described above is provided on the metal mold body, it occupies a considerable part of the space of the metal mold body. Consequently, the space which can be actually utilized for formation of a molded article in the metal mold body is limited to 5 to 20 percent of the entire space of the metal mold body. Besides, not only the space for the slide mechanism section is required for one of a core cavity side metal mold element of the metal mold body but also the space compels the other mold element in pair with the waste of the same space naturally.
As a result, the metal mold body is increased in size and also in weight, and accordingly, there is also a problem that the operation of replacing the metal mold body is very cumbersome.
In the meantime, a forming section of the undercut portion forming slide core described above is formed in an integral relationship with the slide mechanism section including the angular pin hole and the slider block, and there is a problem that, in order to make some change for the undercut portion, either the outer frame mechanism must be disassembled taking much time or the entire metal mold unit including the outer frame mechanism must be replaced. Further, since the forming section of the slide core is formed in an integral relationship with the slide mechanism section, even a little error cannot be absorbed by the same, and accordingly, there is a problem also in engagement of the metal mold.